The invention relates to hand tools of the type that are power driven, and, more particularly, to such a hand tool having a head that can be angled to allow better access to the work material.
Conventional power hand tools, such as drills, cutters and polishers, are limited in their usefulness due to the rigid axial alignment of the drive, power and tool shafts. Many work areas are inaccessible with these tools because the space is limited to less than the tool length, which cannot be shortened by adjusting the angle of the tool head.
Universal joints have proven unworkable for angled operation at speeds of up to 17,000 to 20,000 rpm, or more. Unless universal joints of constant velocity type are used, they produce unacceptably high angular acceleration of the divers components. Even so, under these high velocity conditions the joint components wear out rapidly, due to heat build-up from the friction of components. They also have objectionably high inertia and suffer from complicated construction.
Known flexible power drives are usable only at significantly lower speeds. At high speeds, due to excessive length, when angled, such flexible drives exhibit a whipping action or other distortion which effectively can cause the drive to fail prematurely or even self-destruct by wearing of the shaft against adjacent structures.
Accordingly, the several objects of the invention include provision of a power tool having a novel coupling assembly which connects the motor drive of a power tool to the tool head drive permitting selection of any of several positions of the tool head, either axially or non-axially; which coupling assembly is of constant velocity type; can be securely locked into the selected position for safety in operation; and which safely can be operated with free-wheeling, free-speeding operation to velocities of at least 17,000 to 20,000 rpm with low inertia and without substantial friction, heat build-up, and resultant rapid wear of the coupling or head components. Among other objects of the invention may be noted the provision of such a power tool which is extremely safe and highly reliable in use; which includes redundant securement of the head in a preselected position and which ensures against inadvertent change in head position.
Briefly, a high speed rotary tool apparatus of the hand-held type comprises a body, a tool head, and swivel means adjustably connecting the tool head to the body in preselected angular orientation; the body, including a motor and a high speed rotary drive shaft; the tool head having a tool shaft for carrying a tool to be rotationally driven by the motor at high speed; the swivel means having a power shaft for coupling power from the motor drive shaft to the tool shaft; the power shaft being a single flexible shaft which is flexibly bent when the tool head is at a non-axial angular orientation to the body; and means for guiding and restraining at least one end of the power shaft when bent to prevent whipping or oscillation of the power shaft when rotating.
Other objects and features will be in part apparent and in part pointed out hereinbelow.
The apparatus of the present invention further accomplishes the above-mentioned objects as follows: A flexible wound power shaft is used with crimped sleeves at each end which each fit into a square (or other polygonally shaped) drive. The square drive ends of the power drive in turn are fitted into the female square (or other correspondingly polygonally shaped) drive bushings of the motor drive and the tool head drive, to avoid the whipping action seen at high speeds with conventional flexible drives. A greater path length is provided from the motor drive shaft to the tool shaft than the overall length of the power drive providing gap spacing which accommodates the excess length of the power shaft which results when bent along an angled path. The swivel means provides a coupling assembly having a substantially spherical coupling to allow the tool head to be positioned at one of a plurality of angles or axially in relation to the tool body. Detent mechanisms comprising a plurality of detent balls and recesses allow the coupling assembly to be stablized in a preselected position. Leaf springs resiliently urge the detent balls into their recesses and a spring-loaded locking sleeve forms the outermost tool surface around the coupling mechanism and prevents the detent balls from slipping out of their positions during tool operation, and until a new head position is selected. A safety locking pin and corresponding groove located on the shoulder or forward portion of the spring-loaded locking sleeve prevent the sleeve from inadvertently being axially shifted from its locked position unless the safety pin and groove are in alignment, as accomplished by selectively rotating the sleeve.